1. Field of the Invention
The present invention relates to the inspection of semiconductor substrates during the process of manufacturing semiconductor devices. More particularly, the present invention relates to an apparatus for rotating a sample while the sample is inspected so that the sample can be accurately analyzed.
2. Description of the Related Art
Currently, semiconductor memory devices are being developed at a rapid pace due to the widespread use of equipment, such as personal computers, for processing various types of information. Semiconductor devices must generally perform at high speeds and have the capacity to store large amounts of information. Accordingly, the current art is focused on developing and realizing semiconductor devices having a high degree of integration, response speed, and reliability. To this end, highly precise techniques are required for fabricating today""s semiconductor devices.
More specifically, semiconductor devices are manufactured by repeatedly performing a series of precise unit processes, such as film deposition, patterning and metal wiring processes, on a semiconductor substrate. In addition, various inspection and analysis processes are carried out in the midst of these manufacturing processes. The inspection and analysis processes are carried out with respect to a semiconductor substrate to determine the density of a particular impurity that might be present in or on the surface of a film formed on the substrate, to check whether a bridge phenomenon is present in patterns formed on the substrate, and/or to check whether there is any disconnection in wiring formed on the substrate.
A scanning electron microscope (SEM), a transmission electron microscope (TEM) and a secondary ion mass spectroscope (SIMS) are used for the inspection and analysis processes. The secondary ion mass spectroscope is used for analyzing the composition or the profile of a film/film pattern formed on the semiconductor substrate.
When the profile of a film/film pattern formed on a semiconductor substrate is analyzed by using the secondary ion mass spectroscope, the sample is irradiated with an argon ion beam to thereby etch the sample. As a result, secondary ions are generated from the sample, and these secondary ions are analyzed by the secondary ion mass spectroscope to determine the profile of the film/film pattern. One example of such an analysis process using a secondary ion mass spectroscope is disclosed in U.S. Pat. No. 5,943,548, issued to Kim.
In this technique, the surface of the sample is etched irregularly by the argon ion beam. Such irregularities would limit the resolution of the apparatus in determining the profile of the film/film pattern. This problem can be overcome by rotating the sample. That is, the resolution of the inspection apparatus can be improved by rotating the stage on which the sample is supported.
To this end, the secondary ion mass spectroscope is provided with a sample rotating apparatus, which supports the sample, moves the sample to an analysis position, and rotates the sample. The sample rotating apparatus can move in x-axis, y-axis, and z-axis directions for allowing the sample to be placed at a prescribed coordinates defining an analysis position, and rotates the sample once the sample is located at the analysis position.
The sample rotating apparatus includes a sample stage, a first driving section for rotating the sample stage, and a second driving section for moving the sample stage linearly. The second driving section includes motors for moving the sample stage and the first driving section in x-axis, y-axis , and z-axis directions. The sample is placed on a central area of the sample stage at a position coinciding with the central axis of a rotating shaft of the first driving section. The second driving section moves the sample to the analysis position. Then the sample is rotated by the first driving section, the rotated sample is etched with the argon beam, and the resulting secondary ions are analyzed to determine the profile of a film/film pattern on the sample.
In addition to an analysis chamber in which the sample rotating apparatus is disposed, the inspection and analysis apparatus includes a sub-chamber connected to one side of the analysis chamber. The sample is loaded onto the sample stage in the sub-chamber, and is moved to the sample rotating apparatus provided in the analysis chamber. At this time, the analysis chamber is maintained at a pressure of about 10xe2x88x929 to 10xe2x88x9210 Torr and the sub-chamber is maintained at a pressure of about 10xe2x88x926 to 10xe2x88x927 Torr. That is, the pressure in the sub-chamber is at atmospheric pressure when the sample is loaded in the sub-chamber, and the pressure in the sub-chamber is about 10xe2x88x926 to 10xe2x88x927 Torr when the sample is moved to the analysis chamber. On the contrary, once the sample has been moved into the sub-chamber after the sample has been analyzed, the pressure in the sub-chamber is adjusted to atmospheric pressure to facilitate the unloading of the sample from the sub-chamber. Accordingly, the pressure of the sub-chamber has to be adjusted every time a sample is transferred therethrough, and adjusting of the pressure of the sub-chamber requires a certain amount of time.
Therefore, a plurality of samples are loaded on the sample stage at once in order to make the process efficient. Then, a selected one of the samples is placed at the analysis position, and the profile analysis is carried out with respect to the selected sample. In this case, however, it is difficult to rotate the selected sample. The rotational axis of the drive shaft of the first driving section does not extend through the analysis position while the selected sample is being rotated. This shortens the useful life of the second driving section. That is, the second driving section may rotate the first driving section in a direction identical to the direction rotation of the first driving section so as to prevent the sample from being displaced from the analysis position. At this time, the motors of the second driving section are overloaded. As a result, the secondary ion mass spectroscope has high maintenance and repair costs and limits the efficiency of the overall manufacturing process.
An object of the present invention is to solve the problems of the prior art. Therefore, an object of the present invention is to provide an apparatus that is capable of supporting a plurality of samples, setting a selected one of the samples at an analysis position, and rotating the selected sample about an axis of rotation aligned with the analysis position once the selected sample has been set at the analysis position.
The apparatus for rotating a sample comprises a sample stage for supporting a plurality of samples, position adjusting means for moving the stage such that a selected one of the samples is located at the analysis position, and rotating means for rotating the sample stage and the position adjusting means about an axis that passes through the analysis position such that the selected sample is rotated at the analysis position.
The position adjusting means and rotating means are together mounted to a three-axis drive mechanism. Accordingly, the position adjusting means, rotating means, and sample stage are movable together along three axes orthogonal to one another.
According to another aspect of the present invention, the apparatus for rotating a sample comprises a sample stage for supporting a plurality of samples as spaced from one another along a circle, a moving member supporting the sample stage and movable in a radial direction of the circle such that the sample stage can be located at a position where the circle intersects an analysis position, a rotating cap having a main body disposed on said moving member and supported so as to be rotatable relative to the moving member about a first axis of rotation, a driving mechanism(s) that drives/drive the rotating cap and the moving member, and a rotating stage supporting the moving member and being rotatable about a central axis of rotation passing through the analysis position.
A first driving shaft extending along the central axis of rotation is connected to a lower portion of the rotating stage so as to transmit a driving force that rotates the rotating stage.
The moving member has a main body and a rack disposed on a lower surface of the main body. The rack extends in the radial direction of the circle along which the samples are disposed such that the moving member is moved in the radial direction when a driving force is transmitted to the rack.
The sample stage is mounted to the rotating cap such that the sample stage can be rotated while the circle intersects the analysis position. Thus, a selected sample supported on the stage is set at the analysis position through a combination of the rotational movement of the rotating cap and the linear movement of the moving member. In addition, the rotating cap has first gear teeth at a lower portion of the main body thereof. The first gear teeth are centered around the first axis of rotation such that the rotating cap is rotated relative to the moving body when a driving force is transmitted to the first gear teeth.
The driving mechanism is constituted by a driving gear that is selectively engageable with the first gear teeth of the rotating cap and the rack gear of the moving member, and a second driving shaft that extends through the first driving shaft and is connected to the driving gear.
The sample stage, rotating cap, moving member and rotating stage are together mounted to a three-axis drive mechanism. Accordingly, the sample stage, rotating cap, moving member and rotating stage are movable together along three axes orthogonal to one another.
According to the present invention, a selected sample placed at the analysis position is rotatable about the central axis of rotation aligned with the analysis position. Accordingly, neither the sample rotating apparatus nor the three-axis drive mechanism supporting the sample rotating apparatus is overloaded. Therefore, the analysis process can be selectively or sequentially carried with high efficiency with respect to a plurality of samples and without significantly affecting the useful life of the three-axis drive mechanism.